The present disclosure relates to the field of radiography and, in particular, relates to computer tomography (xe2x80x9cCTxe2x80x9d) scanners. Even more particularly, the present disclosure relates to a system and method for mounting an x-ray tube within a CT scanner.
A typical CT scanner includes a gantry comprising an annular frame for rotatably supporting an annular disk about a rotation, or z-axis of the scanner. The disk includes a central opening large enough to receive a patient upon whom a scan is performed. An x-ray tube is positioned on one side of the disk diametrically across the central opening from an array of x-ray detectors. As the disk rotates, the x-ray tube projects a beam of energy, or x-rays, along a scan plane defined by an x-axis and a y-axis of the scanner, through the patient, to the detector array. By rotating the x-ray source about the z-axis and relative to the patient, radiation is projected through the patient from many different directions. An image of the scanned portion of the patient then is constructed from data provided by the detector array.
The x-ray beam directed toward the detector array emanates from a point in the x-ray tube usually referred to as the focal spot. The accurate generation of imaging data requires that the focal spot of the x-ray tube be suitably aligned with the detector array when installing the tube on the disk of the scanner. Usually the x-ray tube is mounted on the CT scanner and the position of the tube continuously adjusted until the correct positioning of the focal spot is empirically determined. This calibration process usually requires the installer to mount the tube as precisely as possible and then run the machine and measure the output of the detectors to determine if the outputs are optimum, or if adjustments are required.
The process of calibrating the position of the x-ray tube on the CT scanner is time consuming, e.g., two to four hours to complete, and costly. Accordingly, there existed a need for pre-calibrating the focal spot prior to installing the x-ray tube into the CT scanner.
In response, U.S. Pat. No. 5,745,548 to Dobbs et al. disclosed a system and method for pre-calibrating the position of a focal spot of an x-ray tube before installation of the x-ray tube in a CT scanner. The pre-calibration is performed using an interface registration support that receives and supports the x-ray tube on a mount provided in either the pre-calibration system or the scanner. The mount of the pre-calibration system duplicates the mount of the scanner, so that a desired position of the focal spot in the scanner is duplicated in the pre-calibration system. Adjustments in the position of the focal spot with respect to the x, y, and z-axes of the scanner are made through the interface registration support. Once adjustments are made, the x-ray tube and the interface registration support can be installed in the CT scanner without the need for subsequent calibration adjustments.
While Dobbs et al. provides a solution for pre-calibrating an x-ray tube prior to mounting the tube in a CT scanner, there still remains the problem of actually mounting the x-ray tube in a scanner. As is known, CT scanners are relatively large structures (the gantry can be about six feet in diameter for example), and an x-ray tube is relatively heavy and bulky (an x-ray tube can weight two hundred pounds or more, for example). An x-ray tube, therefore, can be awkward for one, or even two service people to handle, lift and mount in a CT scanner.
What is still desired therefore is an improved system and method for mounting an x-ray tube in a CT scanner. Preferably the system and method will make handling, lifting and mounting an x-ray tube in a CT scanner easier and less time consuming. In addition, the system and method will preferably allow for pre-calibrating the x-ray tube prior to mounting the tube in the CT scanner.
The present disclosure, accordingly, provides a system for mounting an x-ray tube in a gantry disk of a CT scanner. The system includes a harness adapted to be secured to the x-ray tube, at least two elongated rods secured to the harness, and two elongated tracks adapted to be secured to the gantry disk such that the tracks extend generally parallel with a z-axis of the CT scanner. Each track includes a channel for receiving the rods in a sliding manner.
The system is designed to make lifting and handling the heavy and cumbersome x-ray tube easier for a person removing or replacing the x-ray tube in a CT scanner. According to one aspect, the system further includes elongated guides adapted to connect to ends of the rods and guide the rods into the channels of the tracks. According to another aspect, the rods are adjustable with respect to the tracks in a direction parallel to the z-axis of the scanner, such that the position of a focal spot of the x-ray tube can be adjusted along the z-axis. According to an additional aspect, the rods are adjustable with respect to the x-ray tube in a direction generally parallel to an x-axis of the scanner, such that the position of the focal spot can be adjusted along the x-axis. According to a further aspect, the rods are adjustable with respect to the x-ray tube in a direction generally parallel to a y-axis of the scanner, such that the position of the focal spot can be adjusted along the y-axis.
The present disclosure also provides a method of mounting an x-ray tube in a gantry of a CT scanner. The method includes securing a harness to the x-ray tube, securing elongated rods to the harness such that the rods extend parallel to an axis of the x-ray tube, attaching elongated guides to ends of the rods, inserting distal ends of the guides into channels of elongated tracks in the gantry of the x-ray scanner, and sliding the guides and the rods into the channels of the tracks. Then the guides are removed from the rods, and stops are secured to ends of the tracks to retain the rods within the channels.
According to one aspect, the position of the x-ray tube with respect to an x-axis and a y-axis of the scanner is calibrated before mounting the x-ray tube in the gantry. According to another aspect, the circumferential position of the x-ray tube with respect to the harness is calibrated before mounting the x-ray tube in the gantry. According to an additional aspect, the position of the x-ray tube with respect to a z-axis of the scanner is calibrated after mounting the x-ray tube in the gantry.